Reflective mask blank for EUV lithography, process for producing the same and mask for EUV lithography

Abstract

Provision of an EUV mask whereby influence of EUV reflected light from an absorber film surface in the peripheral portion of a mask pattern region is suppressed at a time of carrying out EUV lithography; an EUV mask blank to be employed for producing the above EUV mask; and a process for producing the EUV mask blank. A process for producing a reflective mask blank for EUV lithography (EUVL), comprising alternately laminating a high refractive index film and a low refractive index film on a substrate to form a multilayer reflective film for reflecting EUV light and forming an absorber layer for absorbing EUV light on the multilayer reflective film, wherein the process further comprises after formation of the above multilayer reflective film, heating a portion of a surface of the multilayer reflective film outside a portion to be a mask pattern region in a reflective mask for EUV lithography produced by employing the reflective mask blank for EUV, to reduce the reflectivity of the heated portion of the surface of the multilayer reflective film for EUV light.

1. A process for producing a reflective mask blank for EUV lithography (EUVL), comprising alternately laminating a high refractive index film and a low refractive index film on a substrate to form a multilayer reflective film for reflecting EUV light and forming an absorber layer for absorbing EUV light on the multilayer reflective film,
 wherein the process further comprises after formation of the above multilayer reflective film, heating a portion of a surface of the multilayer reflective film outside a portion to be a mask pattern region in a reflective mask for EUV lithography produced by employing the reflective mask blank for EUV, to reduce the reflectivity of the heated portion of the surface of the multilayer reflective film for EUV light 
 wherein the difference of the reflectivity of the heated portion of the surface of the multilayer reflective film for EUV light between before and after the heating is from 10 to 60%. 
 
     
     
       2. The process for producing a reflective mask blank for EUVL according to  claim 1 , wherein the reflectivity for EUV light before the heating is at least 60%. 
     
     
       3. The process for producing a reflective mask blank for EUVL according to  claim 1 , which employs radiation of a light beam or an electron beam for the heating. 
     
     
       4. The process for producing a reflective mask blank for EUVL according to  claim 1 , which employs an exothermic member for the heating. 
     
     
       5. The process for producing a reflective mask blank for EUVL according to  claim 1 , which employs blowing of a preliminarily heated gas for the heating. 
     
     
       6. The process for producing a reflective mask blank for EUVL according to  claim 1 , which further comprises a step of forming on the absorber film an antireflective film for improving the optical contrast at a time of inspecting a mask pattern. 
     
     
       7. The process for producing a reflective mask blank for EUVL according to  claim 1 , which further comprises measuring the reflectivity of a portion of the mask blank outside the mask pattern region for EUV light to confirm that the maximum value of the reflectivity of the portion for EUV light has decreased to be within a desired range before forming the absorbing film. 
     
     
       8. A reflective mask blank for EUVL which is produced by the process according to  claim 1 . 
     
     
       9. The reflective mask blank for EUVL according to  claim 8 , wherein the phase of EUV reflected light from a surface of the absorber film is different from the phase of EUV reflected light from a surface of the multilayer reflective film by from 175 to 185°. 
     
     
       10. The reflective mask blank for EUVL according to  claim 8 , wherein the reflectivity of a portion of a surface of the absorber film outside a portion to be a mask pattern region in a reflective mask for EUV lithography to be produced by employing the reflective mask blank for EUVL, for EUV light is at most 1%, and the reflectivity of a portion to be a mask pattern region for EUV light is more than 1% and at most 15%. 
     
     
       11. A reflective mask for EUV lithography (EUVL) produced by forming a mask pattern in the absorber film of the reflective mask blank for EUVL as defined in  claim 8 . 
     
     
       12. A process for producing a semiconductor integrated circuit comprising carrying out an exposure to an object to be exposed by using the reflective mask for EUVL as defined in  claim 11 . 
     
     
       13. A process for producing a reflective mask blank for EUV lithography (EUVL), comprising alternately laminating a high refractive index film and a low refractive index film on a substrate to form a multilayer reflective film for reflecting EUV light and forming an absorber layer for absorbing EUV light on the multilayer reflective film,
 wherein the process further comprises after formation of the above multilayer reflective film, heating a portion of a surface of the multilayer reflective film outside a portion to be a mask pattern region in a reflective mask for EUV lithography produced by employing the reflective mask blank for EUV, to reduce the reflectivity of the heated portion of the surface of the multilayer reflective film for EUV light, wherein the difference of the reflectivity of the heated portion of the surface of the multilayer reflective film for EUV light between before and after the heating is from 10 to 60% and the heating is carried out under the condition satisfying the following formula:
   Reflectivity (%) for EUV light before heating−9370×heating time (min)×exp (−4370/heating temperature (K))≦1%.
 
 
 
     
     
       14. A process for producing a reflective mask blank for EUV lithography (EUVL) comprising alternately laminating on a substrate at least a high refractive index film and a low refractive index film to form a multilayer reflective film reflecting EUV light, forming a protection film on the multilayer reflective film, and forming an absorber film for absorbing EUV light on the protection film,
 wherein the process further comprises after formation of the protection film a step of heating a portion of the protection film outside a portion to be a mask pattern region in a reflective mask for EUV lithography produced by employing the reflective mask blank for EUVL, to reduce the reflectivity of the heated portion of the surface of the protection film for EUV light 
 wherein the difference of the reflectivity of the heated portion of the surface of the protection film for EUV light between before and after the heating is from 10 to 60%. 
 
     
     
       15. The process for producing a reflective mask blank for EUVL according to  claim 14 , wherein the reflectivity for EUV light before the heating is at least 60%. 
     
     
       16. A process for producing a reflective mask blank for EUV lithography (EUVL) comprising alternately laminating on a substrate at least a high refractive index film and a low refractive index film to form a multilayer reflective film reflecting EUV light, forming a protection film on the multilayer reflective film, and forming an absorber film for absorbing EUV light on the protection film,
 wherein the process further comprises after formation of the protection film a step of heating a portion of the protection film outside a portion to be a mask pattern region in a reflective mask for EUV lithography produced by employing the reflective mask blank for EUVL, to reduce the reflectivity of the heated portion of the surface of the protection film for EUV light, wherein the difference of the reflectivity of the heated portion of the surface of the protection film for EUV light between before and after the heating is from 10 to 60% and the heating is carried out under the condition satisfying the following formula:
   Reflectivity (%) for EUV light before heating−9370×heating time (min)×exp (−4370/heating temperature (K))≦1%.
 
 
 
     
     
       17. The process for producing a reflective mask blank for EUVL according to  claim 14 , which employs radiation of a light beam or an electron beam for the heating. 
     
     
       18. The process for producing a reflective mask blank for EUVL according to  claim 14 , which employs an exothermic member for the heating. 
     
     
       19. The process for producing a reflective mask blank for EUVL according to  claim 14 , which employs blowing of a preliminarily heated gas for the heating. 
     
     
       20. The process for producing a reflective mask blank for EUVL according to  claim 14 , which further comprises a step of forming on the absorber film an antireflective film for improving the optical contrast at a time of inspecting a mask pattern. 
     
     
       21. The process for producing a reflective mask blank for EUVL according to  claim 14 , which further comprises measuring the reflectivity of a portion of the mask blank outside the mask pattern region for EUV light to confirm that the maximum value of the reflectivity of the portion for EUV light has decreased to be within a desired range before forming the absorbing film. 
     
     
       22. A reflective mask blank for EUVL which is produced by the process according to  claim 14 . 
     
     
       23. The reflective mask blank for EUVL according to  claim 22 , wherein the phase of EUV reflected light from a surface of the absorber film is different from the phase of EUV reflected light from a surface of the protection film by from 175 to 185°. 
     
     
       24. The reflective mask blank for EUVL according to  claim 22 , wherein the reflectivity of a portion of a surface of the absorber film outside a portion to be a mask pattern region in a reflective mask for EUV lithography to be produced by employing the reflective mask blank for EUVL, for EUV light is at most 1%, and the reflectivity of a portion to be a mask pattern region for EUV light is more than 1% and at most 15%.